Debian machine makes repeated requests to DNS for <gateway_ip>.in-addr.arpaYou are right. I just read netstat help more carefully and I found who did that. I ran netstat -u -a -n -W -c -p | grep 89.101.160.5 and I found that rsyslog was doing that. But I still do not understand why Debian is trying to make a dns request instead of saying to a requested application that it requests a host ip